Thread-sensing device for a textile machine

ABSTRACT

A thread sensing device has contacts suitable to pass currents for operating thread cutters and the like, which contacts are held apart by a ferromagnetic latch. A thread sensor is coupled to a permanent magnet which is moved when thread breakage occurs to bring the magnet into a position in which it acts on the latch to release the contacts.

United States Patent Santerre et al.

THREAD-SENSING DEVICE FOR A TEXTILE MACHINE Fernand Santerre, Yvelines; Francis Libaud, Hauts-de-Seine, both of France Inventors:

Assignee: La Telemecanique Electrlque, Nanterre,

Hauts de Seine, France Filed: April 28, 1970 Appl. No.: 32,635

Foreign Application l riority Data April 29, 1969 France ..691361l U.S. C1 ..57/8l lnt.Cl. ....D0lg 31/00, DOlh 13/14 Field ofSearch ..57/78, 80, 81, 86; 242/36,

[451 July 18, 1972 [56] References Cited UNITED STATES PATENTS 3,404,524 10/1968 Rajnoha et al ..57/81 3,438,188 4/1969 Boggs ....57/81 3,132,466 5/1964 Preisser ..57/8l 3,420,048 1/1969 Ferri ..57/81 3,262,180 7/1966 Findlow ..57/81 X Primary ExaminerD0nald E. Watkins Attorney-Karl W. Flocks 57 ABSTRACT A thread sensing device has contacts suitable to pass currents for operating thread cutters and the like, which contacts are held apart by a ferromagnetic latch. A thread sensor is coupledto a permanent magnet which is moved when thread breakage occurs to bring the magnet into a position in which it acts on the latch to release the contacts.

11 Claims, 4 Drawing Figures PATENTED JUL 1 8 m2 SHEET 2 OF 2 THREAD-SENSING DEVICE FOR A TEXTILE MACHINE The present invention relates to a thread-sensing device for a textile machine.

It is known that such devices are intended to detect the breakage of a thread in textile machines and, when this happens, either to set off a warning system or, more frequently, to operate thread-cutting units which limit the length of thread brought into the machine.

A number of thread-sensing devices are' known. They are usually constituted by a sensor which is held in its working position by the stretched thread and which swings into a warning position in the event of breakage of the thread or of a reduction in the tension thereof. Certain movable sensors comprise permanent magnets which, when the device is in the warning position act on contacts in sealed capsules. Other swinging sensors are provided with cams which, upon rotation, close contacts held open by a resilient force.

The arrangements of this kind have the drawback of only enabling very low currents to be passed, and this limits their possible uses and in particular calls for use of relays for controlling the thread-cutting means.

According to the present invention a thread-sensing device comprising a thread sensor held in position by the taut thread, a pair of electrical contacts biased towards a closed position but which are normally held in the open position by a latch comprising ferromagnetic material, and a permanent magnet located in proximity to the latch and movable by movement of the' thread sensor upon thread breakage into a position in which the magnetic force exerted by the magnet on the latch is sufficient to move the latter to allow the contacts to close. Conveniently the magnet and the sensor are connected together for common angular movement about a pivotal axis.

In one advantageous embodiment, the permanent magnet is rectilinear and by one of its ends acts on the latch, while in the field of attraction of the other of its ends there'is disposed a ferromagnetic mass the position of which is adjustable.

in such an arrangement, the swinging of the equipment can be completely independent of weight and can be effected by a tractive force acting between the magnet and the ferromagnetic mass. By displacing the latter, it is possible to adjust the reluctance of the magnetic circuit, so that this attraction provides a relatively reduced return force on the sensor of the swinging unit when the latter is in the working position, whereas, with the attraction varying in inverse proportion to the square of the distance between the magnet and the ferromagnetic mass, this attraction increases very rapidly when the swinging action is started, so that the magnet very quickly reaches the position in which it can act upon the latch to release it and to cause the electric contact to be closed.

The attached drawings show, by way of a non-limiting example, one embodiment of the invention.

FIG. 1 is a plan view of a thread-sensing device in accordance with the invention.

FIG. 2 is a section on line ll-ll of FIG. 1.

FIGS. 3 and 4 are sections on lines llllll and lVlV respectively of HO. 2.

The thread-sensing device illustrated in these figures is contained in a case formed from two halves l, which are fitted and held together by means of screws 2. The thread 3 to be monitored passes through thread-guides 4 which are encased in the upper part of the unit when the two parts of the case are fitted together.

The moving part of the equipment swings about a pivot pin 5. It is constituted by a moulded support 6 which carries a permanent magnet 7 and a sensing arm 8 shown in solid lines in its working position and in dash-dot lines in the swung position, as is the rest of the equipment. The sensor 8 is constituted by a suitably bent metal wire which carries at its end a roller 9 which is in contact with the textile thread to be monitored.

The latch is constituted by a mild steel vane 10 mounted in a support 11 having journals 12 to enable it to pivot in bearings formed in the two opposite halves of the case 1.

The contact device comprises a fixed contact 13 constituted by a blade which is embedded between the two halves of the case and which carries a contact piece 14 at one end and a connector 15 at the other. The moving contact is also constituted by a blade 16, bent to U-shape, which likewise terminates in a connector 15 at one end, and the other free end of which, terminating in an inclined portion 17, carries the moving contact piece 18. Apart from the inherent resilience of the blade, the moving contact piece is urged towards the fixed contact piece 13 by a spring 19. In the position illustrated in solid lines, the vane 10 keeps the two contact pieces apart by bearing on a nose 17a at the end of the inclined portion 17.

The vane 10 can be brought into this position by the action of a plunger 20 which slides in one of the two halves of the case and which comprises two branches, one of which, 20a, is directed towards the central portion of the case so as to act on the vane 10, while the other, 20b, is acted upon by a return spring 21 to bring the plunger into the upper position. A second latch or bolt, 22, accommodated in opposite grooves 23 in the two halves of the case, can slide between these two halves and below the thread 3, and includes a cross-member 24 which, when brought into the position 24a, holds the sensor 8-9 in the pressed-down position, that is to say, in the position wherein the magnet 7 is at a distance from the vane 10. The system is then non-active.

On the opposite side of the vane 10, a screw 26, the end of which carries a ferromagnetic pole-piece 27, is engaged in a nut 25 which can be held fast between the two halves of the case. With the equipment in the position illustrated in solid lines, that is to say with the stretched thread 3 holding the sensor in the pressed-down position, if this thread now breaks, the sensor moves into the position 8A firstly because of the effect of weight, and secondly because of the reciprocal attraction between the pole-piece 27 and the end of the magnet nearest thereto. The other end of the magnet consequently moves towards the opposite portion of the vane 10 to that acting as the latch, and causes this vane to swing so that it assumes the position shown in dash-dot lines, releasing the blade 16 and allowing the contacts 14-18 to close. In this latter position, the magnet 7 abuts against the support 11 of the vane 10 and the vane abuts against a transverse portion 28 of the case 1, so that the right hand pole of the magnet cannot contact the pole piece 27 and adhere thereto.

The size of the contacts is such that they can pass a current sufficient to actuate warning means or thread cutters directly.

To re-set the equipment in the working position, the sensor 8 is brought to the position shown in solid lines and is held in this position by the bolt 22 in position 22A when the thread 3 is again pulled taut. Then, pressure applied to the plunger 20 hooks the vane 10 on to the nose 17a again. The thread 3 can then be replaced in position and, when it is again stretched, the equipment can be brought into operation by moving the bolt from position 22A, shown in dash-dot lines, to the posi- 1 tion 22 shown in solid lines.

It will be noted that with equipment of this kind, the two operations necessary for bringing the equipment back into operation, namely separation of the contacts and bringing the sensor back into its active position, are unconnected with each other and achieved by means of the plunger 20 and the bolt 22 respectively. Moreover, the equipment can only be effectively re-set for operation when the thread 3 has resumed its normal tensioned position. Thus, oscillation of the sensor, likely to occur when the textile machine starts up again, is prevented from starting off the thread-cutters again.

Furthermore, when the thread-cutters are of the kind actuated by accumulation of an electric charge in a capacitor, this arrangement gives the capacitors time to recharge to enable the thread-cutting means to operate properly when the machine is put into operation again.

The restoring force acting on the swinging part of the equipment depends upon the position of the pole-piece 27 relative to the magnet 7. This position can be adjusted by turning the screw 26. Thus, the time taken by the equipment to respond when a thread breaks can be adjusted; obviously, the shorter the distance between the magnet 7 and the pole-piece 27 in normal service, the more this time is reduced. Nevertheless, if the distance becomes too small, a return couple would be applied to the swinging part of the equipment and this could be too great to be balanced by the pull on the thread 3 between the threadguides 4.

The invention can be used in particular on spinning machines and on looms dealing with groups of parallel threads, each being controlled by a thread sensor. The invention can also be used on other kinds of filamentary elements, such as electric wires and particularly in machines for coiling such wires.

It will be seen that the embodiment which has been described provides a thread-sensing device which is a contact arrangement permitting the passage of very heavy currents capable of actuating, for example, a plurality of thread-cutting units arranged electrically in series.

We claim:

1. A thread sensing device comprising a fixed electrical contact; a movable contact biased towards said fixed contact by resilient means; a pivoting latch with means to pivot said latch and including ferro-magnetic material movable between an active position in which a portion of said latch is compressed by said resilient means between said movable contact and the latch pivot means, and a rest position wherein said portion of said latch is angularly displaced from the path of said movable contact; a permanent magnet located in proximity to said latch and movable to and out of an operating position in which the magnetic force exerted on said ferro-magnetic material rocks said latch from the active position to the rest position; and a biased thread engaging sensor connected to said permanent magnet and held by thread tension in a first position and which moves in the absence of thread tension into a second position for urging said magnet into said operating position.

2. A thread sensing device according to claim 1 in which said magnet and said sensor are connected together for common angular movement about a pivotal axis.

3. A thread sensing device according to claim 1 in which said permanent magnet is rectilinear and acts through one of its ends on said latch, and a ferromagnetic mass adjustably positionned in the field of attraction at its other end.

4. A thread sensing device according to claim 1 in which a plunger with a resilient return action acts on said latch to bring it into said latching position, said movable contact including an inclined portion cooperating with the active portion of said latch to open said contacts thereby overcoming the force of said resilient return action.

5. A thread sensing device according to claim in which said latch is a mild-steel rocking lever, one end of which is located in the field of attraction of said magnet, whilst the other end constitutes a latch to keep said contacts separated from each other.

6. A thread sensing device according to claim 1 in which the elements of the device are contained in a case constituted by two moulded halves which, when fitted together, hold the various components of the device in position.

7. A thread sensing device according to claim 6 in which the two halves of the case include two thread guides between which can move said thread sensor.

8. A thread sensing device according to claim 7 in which a second hand-operated latch is provided to retain said sensor in the active position.

9. A thread sensing device according to claim 8 in which said second latch can move between said two thread guides to lock said sensor in its active position.

10. A thread sensing device according to claim 1 further characterized by a transverse member in the path of movement of said pivoting latch in contact with said portion of said latch when said latch is in the rest position, one end of said magnet abutting against said latch when said magnet is in operatin position.

11. A t read sensing device according to claim 10 wherein a ferromagnetic mass is adjustably positioned in the field of attraction of said magnet at its other end beyond abutting relationship with said magnet whereby adherence of said magnet and said ferromagnetic mass is prevented. 

1. A thread sensing device comprising a fixed electrical contact; a movable contact biased towards said fixed contact by resilient means; a pivoting latch with means to pivot said latch and including ferro-magnetic material movable between an active position in which a portion of said latch is compressed by said resilient means between said movable contact and the latch pivot means, and a rest position wherein said portion of said latch is angularly displaced from the path of said movable contact; a permanent magnet located in proximity to said latch and movable to and out of an operating position in which the magnetic force exerted on said ferro-magnetic material rocks said latch from the active position to the rest position; and a biased thread engaging sensor connected to said permanent magnet and held by thread tension in a first position and which moves in the absence of thread tension into a second position for urging said magnet into said operating position.
 2. A thread sensing device according to claim 1 in which said magnet and said sensor are connected together for common angular movement about a pivotal axis.
 3. A thread sensing device according to claim 1 in which said permanent magnet is rectilinear and acts through one of its ends on said latch, and a ferromagnetic mass adjustably positionned in the field of attraction at its other end.
 4. A thread sensing device according to claim 1 in which a plunger with a resilient return action acts on said latch to bring it into said latching position, said movable contact iNcluding an inclined portion cooperating with the active portion of said latch to open said contacts thereby overcoming the force of said resilient return action.
 5. A thread sensing device according to claim 1 in which said latch is a mild-steel rocking lever, one end of which is located in the field of attraction of said magnet, whilst the other end constitutes a latch to keep said contacts separated from each other.
 6. A thread sensing device according to claim 1 in which the elements of the device are contained in a case constituted by two moulded halves which, when fitted together, hold the various components of the device in position.
 7. A thread sensing device according to claim 6 in which the two halves of the case include two thread guides between which can move said thread sensor.
 8. A thread sensing device according to claim 7 in which a second hand-operated latch is provided to retain said sensor in the active position.
 9. A thread sensing device according to claim 8 in which said second latch can move between said two thread guides to lock said sensor in its active position.
 10. A thread sensing device according to claim 1 further characterized by a transverse member in the path of movement of said pivoting latch in contact with said portion of said latch when said latch is in the rest position, one end of said magnet abutting against said latch when said magnet is in operating position.
 11. A thread sensing device according to claim 10 wherein a ferromagnetic mass is adjustably positioned in the field of attraction of said magnet at its other end beyond abutting relationship with said magnet whereby adherence of said magnet and said ferromagnetic mass is prevented. 